At a Glance

Why Get Tested?

To help diagnose and monitor autoimmune thyroid diseases and to distinguish these from other forms of thyroid disease; to help guide treatment decisions

When to Get Tested?

When you have a goiter and/or when your other thyroid tests, such as T3, T4, and TSH, indicate thyroid dysfunction; along with a thyroglobulin test when your doctor is using it as a monitoring tool; at intervals recommended by your doctor when you have a known autoimmune thyroid disorder

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Thyroid autoantibodies are antibodies that develop when a person's immune system mistakenly targets components of the thyroid gland or thyroid proteins, leading to chronic inflammation of the thyroid (thyroiditis), tissue damage, and/or disruption of thyroid function. These tests detect the presence and measure the quantity of specific thyroid autoantibodies.

The thyroid is a small, butterfly-shaped gland that lies flat against the windpipe in the throat. The primary hormones that it produces, thyroxine (T4) and triiodothyronine (T3), are vital in helping to regulate the rate at which we use energy – our metabolism. The body has a feedback system that utilizes thyroid stimulating hormone (TSH) to help turn thyroid hormone production on and off and maintain a stable amount of the thyroid hormones in the bloodstream. When thyroid antibodies interfere with this process, they can lead to chronic conditions and autoimmune disorders associated with hypothyroidism or hyperthyroidism, such as Graves disease or Hashimoto thyroiditis.

One or more of the following tests may be performed to help establish a diagnosis of and/or monitor an autoimmunethyroid disorder:

Thyroperoxidase antibody (TPO)—a marker for autoimmune thyroid disease; it can be detected in Graves disease or Hashimotos thyroiditis.

Thyroglobulin antibody (TGAb)—also a marker, this antibody targets thyroglobulin, the storage form of thyroid hormones.

Thyroid stimulating hormone receptor antibodies (TSHRAb)—includes two types of autoantibodies that bind to TSH receptors in the thyroid:

Thyroid stimulating immunoglobulin (TSI) binds to receptors and promotes the production of thyroid hormones, leading to hyperthyroidism.

Thyroid binding inhibitory immunoglobulin (TBII) blocks TSH from binding to receptors, blocking production of thyroid hormones and resulting in hypothyroidism.

TBII is not routinely tested, but TSI is often used to help diagnose Graves disease.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

The Test

How is it used?

Thyroid antibody testing is primarily ordered to help diagnose an autoimmune thyroid disease and to distinguish it from other forms of thyroid dysfunction. It may be ordered to help investigate the cause of a goiter or other signs and symptoms associated with low or high thyroid hormone levels. Testing may be performed as a follow-up when other thyroid test results (such as T3, T4, and/or TSH) indicate thyroid dysfunction.

When a person has symptoms suggesting thyroid disease; when a doctor is considering starting a patient on a drug therapy that has associated risks of developing hypothyroidism when thyroid peroxidase antibodies are present, such as lithium, amiodarone, interferon alpha, or interleukin-2

Has been associated with reproductive difficulties, such as miscarriage, preeclampsia, premature delivery, and in-vitro fertilization failure

Thyroglobulin antibody

TgAb

Thyroid cancer; Hashimoto thyroiditis

Whenever a thyroglobulin test is performed to see if the antibody is present and likely to interfere with the test results (e.g., at regular intervals after thyroid cancer treatment); when symptoms of hypothyroidism are present

When a person has symptoms of hyperthyroidism; to monitor the effectiveness of anti-thyroid therapy

If a pregnant woman has a known autoimmune thyroid disease (such as Hashimoto thyroiditis or Graves disease) or has another autoimmune disorder and thyroid involvement is suspected, then one or more of the thyroid antibodies may be ordered early in the pregnancy and then again near the end. These tests are used to help the doctor determine whether the baby may be at risk of thyroid dysfunction since thyroid antibodies can cross the placenta and cause hypothyroidism or hyperthyroidism in the developing baby or newborn.

Thyroid antibody testing may also be ordered when a person with another autoimmune disorder has symptoms of thyroid dysfunction and/or when she has reproductive difficulties that the doctor suspects may be associated with autoantibodies.

What does the test result mean?

Negative test results means that the autoantibodies are not present in the blood at the time of testing and may indicate that symptoms are due to a cause other than autoimmune. However, a certain percentage of people who have autoimmune thyroid disease do not have autoantibodies. If it is suspected that the autoantibodies may develop over time, as may happen with some autoimmune disorders, then repeat testing may be done at a later date.

In general, the presence of thyroid antibodies suggests that there is autoimmune thyroid involvement and the higher the level, the more likely that is. Rising levels may be more significant than stable levels as they indicate an increase in autoimmune activity. All of these antibodies, if present in a pregnant woman, can increase the risk of hypothyroidism or hyperthyroidism in the developing baby or newborn.

If thyroglobulin antibodies are present when the doctor is monitoring thyroglobulin levels, they will interfere with the test results. This may mean that the doctor will not be able to use thyroglobulin as a tumor marker for thyroid cancer. If thyroglobulins antibodies are being used as a monitoring tool and have stayed high or dropped low initially but are increasing over time, then it is likely that the treatment has not been effective and the condition is continuing or recurring. If levels are falling and/or have fallen to low or undetectable levels, then it is more likely that the therapy has been effective.

A certain percentage of people who are healthy may be positive for one or more thyroid antibodies. The prevalence of these antibodies tends to be higher in women, tends to increase with age, and indicates an increased risk of developing thyroid disease in the future. If an individual with no apparent thyroid dysfunction has a thyroid antibody, the doctor will track her health over time. While most may never experience thyroid dysfunction, a few may develop it.

Is there anything else I should know?

The sensitivity and specificity of thyroid antibody testing is improving but is still not as good as doctors would like it to be. All of the thyroid antibody tests have changed over time. This is part of the reason that the tests have historically acquired many different names. There are also many distinct methodologies and each has different reference (normal) ranges. If someone is having serial testing done for monitoring purposes, it is best to have test done by the same laboratory each time, using the same methodology.

Common Questions

1. Are thyroid antibodies part of routine testing?

No, they are usually only indicated when a person has an enlarged thyroid or symptoms suggesting thyroid dysfunction. Routine screening of the thyroid is usually accomplished using thyroid tests such as TSH and T4.

2. Can thyroid antibody testing be done in my doctor's office?

Though a blood sample may be collected at your doctor's office, it will likely be sent to a laboratory for testing. These tests require specialized equipment to perform and are not offered by every laboratory. It may take several days for the results to be available.

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Elsewhere On The Web

Article Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Slatosky, J. et. al. (2000 February 15). Thyroiditis: Differential Diagnosis and Management. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/20000215/1047.html through http://www.aafp.org.

(2002 September, Updated). Hashimoto's Disease: What It Is and How It's Treated. Familydoctor.org [On-line information]. Available online at http://familydoctor.org/548.xml through http://familydoctor.org.

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This article was last reviewed on September 14, 2012. | This article was last modified on February 24, 2015.

The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.

The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.